The tunnel constitutes the easternmost section of the Drammen Line and runs below the central business district of Oslo.

The tunnel constitutes the easternmost 3,632 metres (2.257 mi) of the Drammen Line, and runs between Oslo S and Skøyen.

The station has four tracks and two 250-metre-long (820 ft) island platforms, serving the central business district of Oslo.

Elisenberg Station, located in Frogner, is partially built, including a 220-metre-long (720 ft) island platform and one of the entrances.

[12] Led by Axel Grenholm,[13] the committee recommended one of two alternatives: either establish a branch from the Drammen Line and built a tunnel under the city center, in which all trains would terminate at Oslo Ø.

Olsens gate, with an intermediate station close to the location of Oslo V.[14] The proposed tunnel would be 1,660 metres (1.03 mi) long and largely run through clay, making construction more difficult and expensive.

[16] In 1950, they presented a new report, which recommended that a new route for the tunnel be considered to ease construction and increase safety.

It was a compromise between the Norwegian State Railways' need for a line as straight as possible, and Oslo Municipality's demands that the construction should not be a risk to buildings in the area.

[22] However, it felt that the tunnel should be longer and intersect with the Drammen Line at a point between Skarpsno and Skøyen, and build a second station at Frogner.

[23] The proposal was presented to the Parliament of Norway on 4 November 1961, along with several other matters related to rail transport investments.

Consultants included Ingeniørene Bonde & Co., Peer Qvam's arkitektkontor and the Norwegian Geotechnical Institute.

The work expanded the station from two to four platforms, thus increasing the applied capacity for the whole tunnel from 16 to 24 trains per direction per hour.

[33] Between 2008 and 2012, the Norwegian National Rail Administration is performing a major upgrade to the section between Lysaker and Etterstad, including the Oslo Tunnel.

One proposal from the National Rail Administration calls for a separate commuter train station to be built underground, at the location of Oslo Bus Terminal, within walking distance of Oslo S. This proposal involves the line connecting to the existing route before reaching Nationaltheatret.

[10] The lobby organisation Norsk Bane have called for a line to run further north, and serve Majorstuen, where there is a major metro and tramway hub.

Norsk Bane also call for the tunnel to be built for higher speeds, and state that it is necessary to build high-speed rail to Bergen and Stavanger.